The present invention relates generally to an aircraft fuel training apparatus. More specifically, it relates to a fuel trainer which uses a fuel look-alike with a high flash point and low viscosity.
Aircraft training devices school pilots and maintenance personnel in the operation, maintenance and service of aircraft and their systems without the expense, inconvenience and danger of training on actual aircraft. These training devices are often mockups or demonstrative apparatus of either full or scale size which isolate a particular system and simulate its function. Aircraft fuel systems are among the simulated systems. A typical aircraft fuel trainer includes fuel tanks and associated fuel lines and pumps to connect and transfer fuel between them. Visual indicators, switches and other hardware are also included. Actual components are used to best simulate the operation of the fuel system.
One prior method was to use actual aircraft fuel, such as JP4/5, in the simulation. Although this provided an accurate simulation, it was disadvantageous due to the fire hazard associated with the low flash point of the fuel. JP4 and JP5 have flash points of 135.degree. F. and 150.degree. F. respectively, making them "hazardous" materials under the Department of Transportation definition, which includes liquids with flash points below 200.degree. F.
To avoid the fire hazard associated with actual aircraft fuel, fuel "look-alikes" with higher flash points have been used instead. For example, U.S. Pat. No. 5,152,688 to Cellini discloses the use of SEMTOL 85 {.TM.}, available from Witco Chemical Corporation; and PENRECO {.TM.} white mineral oil #2260, available from Pennzoil Products Company. These liquids have flash points of 365.degree. F. and 260.degree. F. respectively.
Although the use of look-alikes such as SEMTOL-85 {.TM.} and PENRECO {.TM.} has improved safety, the disadvantage has been an inaccurate simulation due to their viscosity. An accurate simulation requires a fluid with a viscosity, specific gravity and dielectric constant similar to that of aircraft fuel. SEMTOL 85 {.TM.} has a specific gravity of 0.803 and a dielectric constant of approximately 25-30 KV/cm2. Thus for these two properties it is similar to JP4, which has a specific gravity of 0.76 and a dielectric constant of 25-30 KV/cm2; and JP5, which has a specific gravity of 0.81 and a dielectric constant of 25-30 KV/cm2. However, its viscosity of 16 cs (at 104.degree. F.) is many times greater than 0.9 cs and 1.4 cs for JP4 and JP5 respectively (at 100.degree. F.). This also holds true for PENRECO, which has a viscosity of 4.3 cs.
This high viscosity results in a greater fluid pressure drop across the system components and thus an inaccurate simulation. To have both an accurate simulation and safety would require a fluid with a low viscosity and a high flash point. Insofar as flash point generally increases with viscosity, a look-alike with all of the desired characteristics has heretofore not been used.